A major challenge for triage of casualties under tactical field care is the absence of lightweight, accurate, intuitive body imaging techniques for trauma patients. Casualty presentation and evaluation on the battlefield or to natural disasters can be complex. This complexity may be further enhanced by the austere diagnostic environments common to theaters of battle. Under these conditions, spinal fractures can be difficult to identify, and pneumothorax issues may be routinely difficult or impossible to accurately diagnose via breath sounds and percussion. Bleeding in the peritoneal, pleural, or pericardial spaces may also occur without obvious clinical warning signs. Distracting obvious open bone injuries and acute altered mental status or unconsciousness can further conceal critical injuries. Accurate triage is essential to allow a medic to stabilize the casualty for transport or to call in a forward surgical team.
Current medical imaging techniques are expensive, often expose patients to potentially harmful radiation, and are mostly non-portable. X-Rays require bulky installation and heavy lead shielding, which as a practical matter is normally only accessible within a clinic or hospital. For example, to fly a portable x-ray or fluoroscopy machine to a remote military base would require one-third the cargo capacity of a Chinook helicopter. Three dimensional (“3-D”) imaging from x-rays remains undeployed and requires task-specific a-priori data. Mobile Computed tomography (“mCT”) offers high resolution imaging, eliminating shielding needs and is smaller than standard CT imaging systems while still providing 3-D imaging capability. CT is especially helpful in acute head trauma situations for identifying fresh intracranial or subdural bleeding. However, the smaller mobile gantries cannot image the entire body—only the head and neck—and still involve exposing the patient to radiation. Also, because of its large size, mCT is only suitable for intra-hospital use with stable, sedated patients in neurosurgery and intensive care wards. Additionally, contrast agents may be necessary for proper diagnosis. Magnetic Resonance Imaging (“MRI”) does not use ionizing radiation, but the large magnet installation largely relegates MRI systems to hospital-based diagnosis methods. The use of MRI is also undesirable in cases involving hemodynamic compromise, making it unfit for many casualty presentations. Furthermore, the time require for using these modalities is substantial, which renders each unsuitable for a quick field assessment or triage.
Ultrasound is a promising option for mobile trauma diagnostics. Ultrasound is widely accepted as a means to visualize internal organ space, and can be used concurrently with other treatments and diagnostics. Ultrasound is a cheaper modality than x-ray, mCT, or MRI, and is portable enough to be packed in a small bag. However, ultrasound is limited to two-dimensional (“2-D”) images that require significant expertise to interpret. Focused Assessment with Sonography in Trauma (“FAST”) is routinely used for quick assessment of blunt and penetrating chest and abdominal trauma, and is specifically indicated for identifying potential pericardial effusion, intraperitoneal bleeding, or bleeding in the pleural space (hemothorax). Assessment of pneumothorax is available in an extended-FAST (“E-FAST”) protocol.
In civilian settings, FAST has been used to decrease CT and diagnostic peritoneal lavage without risk to the patient. In a military setting, ultrasound has been proven useful in single-surgeon hospital-based trauma studies. Recently, ultrasound has been deployed in the theater experimentally in certain battalions with great success in 2-D soft tissue imaging. This deployment of ultrasound has benefited the local civilian war wounded as well. However, ultrasound has been relegated to non-emergent diagnostics such as shrapnel identification in wounds or late identification of closed limb fractures at the bedside. It has recently been suggested that ultrasound could be used to address bone fracture identification in the field, but this would require that the user have extensive specialized training and expertise.
Accurate diagnoses are difficult and yet most essential with a complicated initial presentation in the field or in a hospital emergency department. However, to date no available modality has proven able to reliably detect bone skeletal trauma—which is often undetectable by a physical examination—along with other potential life-threatening internal visceral injuries that produce air and blood collections in the patient.